Systems and methods for intra-shot dynamic adjustment of LIDAR detector gain

ABSTRACT

Systems, methods, and computer-readable media are disclosed for a systems and methods for intra-shot dynamic LIDAR detector gain. One example method my include emitting, by an optical ranging system at a first time, a first light pulse. The example method may also include increasing, after the first time, a sensitivity of a photodetector of the optical ranging system from a first sensitivity at the first time to a second sensitivity at a second time. The example method may also include decreasing the sensitivity of the photodetector of the optical ranging system from the second sensitivity at third time to the first sensitivity at a fourth time, wherein the fourth time is after the photodetector receives return light based on the first light pulse. The example method may also include emitting, by the optical ranging system at the fourth time, a second light pulse.

BACKGROUND

In a conventional LIDAR system, the return power (for example, power oflight reflected back towards the LIDAR system from an object in theenvironment) may vary considerably depending on range, reflectivity,angle of incidence, surface features, and other factors. In order toaccurately image a wide variety of surfaces as found in uncontrolledenvironments (for example, outdoors) it may be desirable to construct aLIDAR system that can detect objects in of as wide of a reflectivityrange as possible at as far a distance as possible without saturatingthe detector or rendering it insensitive to low-reflectivity surfaces.This may be difficult when attempting to range an object of very lowintensity at a very short distance, as it may be difficult todifferentiate a low-intensity return from an object in the environmentfrom internal reflections from the LIDAR system itself. Conventionalsolutions to this problem may include using high-cost high dynamic rangereceivers, placing a minimum range limit that is often meters away fromthe sensor, rendering a not-inconsiderable swathe of sensing area blindto all returns, and using high-complexity signal processing todifferentiate between internal reflections and returns from surfacesexternal to the sensor, which may increase the processing requirementsand may still be prone to uncertainty.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingdrawings. The drawings are provided for purposes of illustration onlyand merely depict example embodiments of the disclosure. The drawingsare provided to facilitate understanding of the disclosure and shall notbe deemed to limit the breadth, scope, or applicability of thedisclosure. In the drawings, the left-most digit(s) of a referencenumeral may identify the drawing in which the reference numeral firstappears. The use of the same reference numerals indicates similar, butnot necessarily the same or identical components. However, differentreference numerals may be used to identify similar components as well.Various embodiments may utilize elements or components other than thoseillustrated in the drawings, and some elements and/or components may notbe present in various embodiments. The use of singular terminology todescribe a component or element may, depending on the context, encompassa plural number of such components or elements and vice versa.

FIG. 1A depicts an example process, in accordance with one or moreexample embodiments of the disclosure.

FIGS. 1B-1C depict example user-defined functions, in accordance withone or more example embodiments of the disclosure.

FIGS. 2A-2C depict exemplary circuitry, in accordance with one or moreexample embodiments of the disclosure.

FIG. 3 depicts an example method, in accordance with one or more exampleembodiments of the disclosure.

FIG. 4 depicts a schematic illustration of an example systemarchitecture, in accordance with one or more example embodiments of thedisclosure.

DETAILED DESCRIPTION

Overview

This disclosure relates to, among other things, systems and methods forintra-shot dynamic adjustment of LIDAR detector gain. In someembodiments, the systems and methods described herein may moreparticularly relate to dynamically adjusting the gain of a photodetectorin an optical ranging system in order to vary the sensitivity of thephotodetector to return light based on the amount of time that haspassed since a corresponding light pulse was emitted from the opticalranging system (and based on the distance that the emitted light pulsehas traveled from the optical ranging system). In some instances, theoptical ranging system may be a LIDAR system (for simplicity, referencemay be made hereinafter to a LIDAR system, but other optical rangingsystems could be similarly applicable). In some instances, thephotodetector may be an Avalanche Photodiode (APD), and may morespecifically be an APD that operates in Geiger Mode (however, othertypes of photodetectors may also be used). This dynamic gain adjustmentmay be performed in order to detect objects of as wide of a reflectivityrange as possible at as far a distance as possible without saturatingthe receiver or rendering it insensitive to low-reflectivity surfaces.Using such a dynamic gain to detect objects of as wide of a reflectivityrange as possible may allow the LIDAR system to more accurately image awide variety of surfaces as found in uncontrolled environments (forexample, outdoors). One example of a conventional practice foraddressing the aforementioned may involve changing the gain of thephotodetector on a per-shot basis (for example, per light pulse emittedfrom the emitter device). This, however, may result in some percentageof return light being be outside the useful representation range of thedetector, with “low gain” shots (for example, light pulses that areaccompanied by a lower bias voltage being applied to the detector toresult in a lower gain of the photodetector) potentially resulting inthe photodetector unable to see return light from non-reflective objectsin the environment, and “high gain” shots (for example, light pulsesthat are accompanied by a higher bias voltage being applied to thedetector to result in a higher gain of the photodetector) saturating thephotodetector. A photodetector being unable to “see” a non-reflectiveobject may be indicative of the fact that non-reflective objects mayreflect little to none of the emitted light back to the LIDAR system. Asa result of this, little to no photons will reach the photodetector. Anyphotons that are able to reach the photodetector may beindistinguishable from mere environmental noise (for example strayphotons that are detected by the photodetector that do not originatefrom the LIDAR system), and thus the non-reflective object may beeffectively invisible to the photodetector during the low gain shots.Another conventional practice builds on this previous conventionalpractice by producing a high-dynamic-range detector by combining “high”and “low” gain shots and interspersing them throughout a LIDAR sweep.This, however, may result in many shots that contain limited or noinformation. Another alternative conventional solution to this mayinvolve using a detector with native high dynamic range, but thisconventional solution may entail great cost and complexity, as the noisefloor of the detector may need to be extremely low for the photodetectorto be useful.

Given these downfalls to some of the conventional approaches toaddressing the phenomenon that return light power varies depending onrange, the systems and methods described herein may provide solutions todynamically adjust the detector sensitivity as emitted light from theLIDAR system travels further from the LIDAR system. These adjustmentsmay be performed based on a user-defined function. In some embodiments,the gain of the photodetector may be dynamically adjusted by adjustingthe bias voltage applied to the photodetector (the gain of thephotodetector may be a function of the bias voltage applied to thephotodetector). The dynamic application of the bias voltage may beperformed using a number of different methods. One example may includeusing a high-speed digital to analog converter (DAC) to produce acontinuous gain waveform. A second example may include an analogmultiplexor with two or more voltage selections for a discrete levelgain waveform. These two examples should not be taken as limiting, andany number of additional methods for dynamically changing the appliedbias voltage may also be used.

In some embodiments, the dynamic adjustment of the photodetector gain(for example via the applied bias voltage) may begin with setting thebias voltage at or below a threshold value for a time frame in betweenemitting a light pulse from the emitting device (for example laserdiode) and the light pulse exiting the interior of the LIDAR system andentering the environment. Setting the bias voltage of the photodetectorto be at or below this threshold value may result in the photodetectoroperating in a linear mode (for example with a linear gain). This may bein contrast to operation of a photodetector in Geiger Mode, for example,which may involve the photodetector operating at a much higher gain (forexample on the order of 10⁵ or 10⁶). For example, the bias voltage maybe reduced to 20V or lower. A linear-mode photodiode may respond toincident light by allowing an amount of current proportional to anintensity of the incident light intensity to flow as determined by again function. A photodiode in Geiger mode may instead avalanche withincident light and continue to pass current until quenched (that is,until it's applied bias voltage is lowered to below the photodiode'sbreakdown voltage). Operation of the photodetector in linear mode mayresult in the photodetector being insufficiently sensitive to achievelong-range detection using eye-safe photonic sources (for examplesources that may be used in autonomous vehicle systems, such as theemitting device 102, emitter 402, and/or any other emitting device,emitter, and the like described herein). This may be because it may takemany photons to achieve a signal that is higher than the noise floor ofthe system when the photodiode is operating in linear mode, whereas aGeiger-mode photodiode may be set to avalanche upon the incident of asingle photon, and the amplitude of its response may be independent ofthe number of photons that have struck it. This operation of thephotodetector in linear mode during this particular time frame may serveto prevent return photons that may have been reflected internally to theLIDAR system back towards the photodetector from being recognized assignals indicative of returns from objects in the environment. Asdescribed above, such returns may be difficult to distinguish fromreturns that originate from low-reflective objects close to the LIDARsystem. Thus, these internal reflections may result in undesirableinformation for the LIDAR system.

In some embodiments, subsequent to the emitted light exiting the LIDARsystem, the gain of the photodetector may be increased to allow thephotodetector to detect when the emitted light reflects from objects inthe environment and back towards the LIDAR system. In some instances,the gain of the receiver may be increased based on a user-definedfunction (example functions may be depicted in FIGS. 1B-1C). Thefunction may define what the bias voltage of the photodetector should beset to at any given time in the timeframe between the emitted lightentering the environment and traversing towards the maximum detectingrange of the photodetector. For example, the bias voltage applied to thephotodetector may be dynamically adjusted over time instead of simplybeing increased to a maximum value immediately following the emittedlight entering the environment. As a first example, the bias voltage maybe steadily increased as the time since the emitted light exited theLIDAR system also increases (up until a time at which any return lightreceived by the photodetector may originate from a maximum detectionrange of the LIDAR system, and the bias voltage detector may be broughtto or below the threshold again as described above). As a secondexample, the bias voltage may be increased to a maximum value at a timeat which return light received by the photodetector may originate beforethe maximum range, and then may be decreased. That is, the bias voltagemay be increased to a maximum value corresponding to a time at whichreturn light from the environment may originate from a particular regionof interest in the environment. For example, it may be desirable toensure that the detector is more sensitive to particular regions in theenvironment of the LIDAR system for a number of reasons. As a fewnon-limiting examples, there may be a known object of interest in theregion or it may not be known if objects are in the region, but it maybe desired to determine if objects do exist. As a third example, thegain may be altered based on external factors. For example, one externalfactor may include the ambient light of the LIDAR system (for examplethe gain may be minimized when the ambient light is greater during abright day). Additional examples may include weak returns from dust orrain in the air, or secondary returns from windows, or extremetemperatures causing spontaneous avalanches of the photodetector. Theabove examples are not intended to be limiting, and the gain of thephotodetector may be dynamically adjusted based on any other form ofuser-defined function as well.

In some embodiments, in addition to reducing the bias voltage of thephotodetector to or below the threshold value while the emitted light istraversing the interior of the LIDAR system, the bias voltage may alsobe reduced to or below the threshold value at a second time. This secondtime may include a time at which return light from the environment maycorrespond to light that is returning from a maximum detecting range ofthe photodetector. That is, if the maximum detecting range of thephotodetector is known, it may be possible to determine when lightreflecting from that maximum distance may return to the LIDAR system andbe detected by a photodetector (for example, given that the speed oflight is known). The maximum range of the photodetector, for example,may be a factor of the rate at which the emitting device is emittingsubsequent light pulses, but also may depend on other factors as well.An example of a maximum range may be 320 meters, but any other maximumrange may also be possible. The purpose of also effectively blinding thephotodetector at the maximum detecting range of the LIDAR system may beto prevent range aliasing. Range aliasing may be a phenomenon wherelight returns beyond the maximum range are detected as if they werewithin the range of the LIDAR system (for example, the light may beincorrectly identified as return light from a subsequent light pulseemitted from the LIDAR system). This may lead to inaccurate rangeinformation regarding objects in the environment of the LIDAR system.Thus, for each emitted beam of light it may be desirable to ensure thatthe detector may only be detecting return light within the maximum rangewindow of the LIDAR system. In some instances, the bias voltage of thephotodetector may also be reduced to or below the threshold value atother times not described herein. For example, operation of a photodiodein linear mode may be useful in situations when a photodiode inavalanche mode is spontaneously avalanching at too great a rate to beuseful, and the signal power of the return is high enough to warrantlinear mode. For example, this may be the case in a scenario where aclean data with a single scan of the environment at close range may berequired.

In some embodiments, the above-mentioned function may be user-definedand may either be fixed or may change with successive shots (a “shot”may refer to a pulse of light emitted by the LIDAR system). A fixedfunction may involve the same function being used for each successivelight pulse that is emitted from the LIDAR system (for example eachsuccessive shot). That is, the gain may increase and or decrease in thesame manner at the same times with each successive light pulse. However,in some embodiments, the function may also be varied among some or allof the successive shots. For example, a first function may be used for afirst shot, and a second function that is different than the firstfunction may be used for a second shot. The use of different functions,for example, may be a useful way to increase dynamic range of the LIDARsystem. That is, one shot may pick up bright objects in the environment,and the second may be used to identify dim objects in the environment.The sensitive shot can hide high-reflective objects in the responses ofthe dim objects, since the photodiode may not have recovered in time torespond to the highly reflective objects. By sweeping a single scanthrough various gains, as many returns as possible may be gathered, notjust the strongest or the closest or the ones far enough apart that thephotodiode has time to recover.

In some embodiments, the systems and methods described herein may beimplemented as an open-loop system. That is, the detector gain functionmay be fixed as described above and the dynamic gain adjustment of thephotodetector may be iteratively performed in the same manner upon everylaser firing of the LIDAR system. In some embodiments, however, thesystems and methods described herein may also be implemented as aclosed-loop system. That is, the detector gain function may be alteredbased on information received back from the environment, such as timinginformation with respect to the timing of return light reflected fromobjects in the environment. As one example, the gain of the detector maybe altered to peak at a particular time where it is determined fromprevious returns that an objects may exist in the environment. Thisalteration in the gain function may be performed so that moreinformation can be obtained about this identified object, rather thanmaximizing the gain where it may have been determined previously thatobjects are not present. However, the gain may be altered in any numberof other manners based on any other number of criteria as well. Forexample, monitoring the response of the system in real-time may make itpossible to adjust the gain in the middle of a shot based on adetermined noise floor level (ambient light). This may also be used as aform of active quenching, rapidly drawing down the applied bias voltageafter an avalanche and reconstituting it in order to increase theresponse rate of the photodiode.

With reference to the figures, FIG. 1A includes a schematic diagram ofan example process 100 for an exemplary LIDAR system 101 that may employdynamic photodetector gain adjustments as described above. Withreference to the elements depicted in the process 100, the LIDAR system101 may include at least one or more emitting devices 102, one or moredetector devices 103, one or more circuits 104, and/or one or morecontrollers 105. The LIDAR system 101 may also optionally include one ormore emitter-side optical elements 113 (for example, which may be thesame as optical element(s) 404 as described with respect to FIG. 4 )and/or one or more receiver-side optical elements 114 (for example,which may be the same as optical element(s) 408 as described withrespect to FIG. 4 ). Additionally, external to the LIDAR system 101 maybe an environment 108 that may include one or more objects (for exampleobject 107 a and/or object 107 b). Hereinafter, reference may be made toelements such as “emitting device,” “detector device,” “circuit,”“controller,” and/or “object,” however such references may similarlyapply to multiple of such elements as well.

In some embodiments, an emitting device 102 may be a laser diode foremitting a light pulse (for example, the emitter 402 as described belowwith reference to FIG. 4 ). A detector device 103 may be a photodetector(for example, the detector 406 as described below with reference to FIG.4 ), such as an Avalanche Photodiode (APD), or more specifically an APDthat may operate in Geiger Mode (however any other type of photodetectormay be used as well). It should be noted that the terms “photodetector”and “detector device” may be used interchangeably herein. A circuit 104may be circuitry connected to the detector device 103 that may be usedto dynamically alter the gain of the detector device 103 by applyingvarying bias voltages to the detector device 103. The gain of thedetector device 103 may be based on the bias voltage that is applied tothe detector device 103. The circuit 104 may be described in more detailin FIGS. 2A-2C below. The controller 105 may be a computing system (forexample, the computing portion 413 described below with respect to FIG.4 ) that may be used to control any of the operations described withrespect to process 100. For example, the controller 105 may be a part ofa closed-loop system in which the gain set by the circuit 104 may beadjusted based on return light from the environment 108. However, insome instances the LIDAR system 101 may be an open-loop system and thecircuit 104 may alternatively adjust the gain of the photodetector 103based on a fixed, user-defined function, and the circuit 104 mayfunction without the use of the controller 105. Finally, an object 107 aand/or 107 b may be any object that may be found in the environment 108of the LIDAR system 101 (for example, object 107 a may be a vehicle andobject 107 b may be a pedestrian, but any other number or type ofobjects may be present in the environment 108 as well).

In some embodiments, the steps of the process 100 may proceed asfollows. The process 100 may begin with an emitting device 102 emittinga light pulse 106. The light pulse 106 may not immediately exit theLIDAR system 101 and enter the environment 108, but may instead traversethe interior of the LIDAR system 101, which may be shown as distance d₁in the figure. That is, the light pulse 106 may travel distance d₁ fromthe emitting device 102 to an interface 109 between the interior portionof the LIDAR system 101 and the environment 108. As described above,while light is traversing the interior of the LIDAR system 101, it maybe possible for some of the light pulse 106 to internally reflect. Thatis, the light pulse 106 may reflect from elements internal to the LIDARsystem 101 and/or at the interface 109 back towards the detector device103. To mitigate or prevent the photodetector 103 from registering suchinternal reflections, the detector device 103 may be effectively blindedfor a period during which any portion of the light pulse 106 might betraversing up to the distance d₁ and then back to the detector device103 As described above, it may be undesirable for the detector device103 to register these internal reflections because they may be difficultto distinguish from return reflections originating from low-reflectivityobjects that are in the environment 108 (external to the LIDAR system)in close proximity to the LIDAR system 101. Blinding the detector device103 may include lowering a bias voltage of the detector device 103 to beat or below a lower threshold voltage value. For example, the lowerthreshold voltage value may be 20V, but any other voltage may similarlybe applicable. Lowering the bias voltage of the detector device 103 toat or below this lower threshold voltage value may place the detectordevice 103 in a linear mode of operation in which the gain of thedetector device 103 is linear. A linear-mode photodiode may respond toincident light by allowing an amount of current proportional to anintensity of the incident light intensity to flow, as determined a gainfunction. A photodiode in Geiger mode may instead avalanche withincident light and continue to pass current until quenched (that is,until it's applied bias voltage is lowered to below the photodiode'sbreakdown voltage). Operation of the detector device 103 in linear modemay result in the detector device 103 being insufficiently sensitive toachieve long-range detection using eye-safe photonic sources (forexample sources that may be used in autonomous vehicle systems, such asthe emitting device 102, emitter 402, and/or any other emitting device,emitter, and the like described herein). This may be because it may takemany photons to achieve a signal that is higher than the noise floor ofthe system when the photodiode is operating in linear mode, whereas aGeiger-mode photodiode can be set to avalanche upon the incident of asingle photon, and the amplitude of its response may be independent ofthe number of photons that have struck it.

In some embodiments, subsequent to the light pulse 106 reaching theinterface 109 of the interior portion of the LIDAR system 101 andentering into the environment 108 (for example, corresponding to a timeafter which any return light reflected internal with the LIDAR system101 would be received by the photodetector 103), the bias voltageapplied to the detector device 103 may again be increased above thelower threshold voltage value. This may correspondingly increase thegain of the detector device 103 such that the detector device 103 may becapable of detecting an amount of return photons from the environment108 that is distinguishable from merely environmental noise. Forexample, the bias voltage may be increased above the 20V threshold.Additionally, as the light pulse 106 traverses through the environment108, the gain of the photodetector 103 may be increased or decreased(through a corresponding increase or decrease in the bias voltageapplied to the detector device 103) over time based on a user-definedfunction. As one non-limiting example, a user-defined function may looksimilar to the function 152 depicted in FIG. 1B.

In FIG. 1B, the x-axis may represent time, and the y-axis may representa bias voltage that may be applied by the circuit 104 to thephotodetector 103 at the corresponding times on the x-axis (for exampleT₂, ΔT₃, T₄, ΔT₅ and T₆). The gain of the detector device 103 may bebased on the bias voltage, so the portions of the function where theapplied bias voltage is increasing may correspond to an increase in thegain of the detector device 103. The function 152 may include a lowerthreshold value 156 (for example which may be the same as the lowerthreshold voltage value) and an upper threshold value 159, which may bea maximum bias voltage applied to the photodetector 103. As depicted inFIG. 1B, the function 152 may begin at time T₁ when the light pulse 106is emitted from the emitting device 102. As shown in the function 152,the bias voltage applied to the photodetector 103 may be at or below thelower threshold value 156 until time T₂. Time T₂ may correspond to atime at (or after) which light that has reached the interface 109 of theLIDAR system 101 would be received at the photodetector 103 (forexample, reflected from the interface 109 back to the photodetector103). Subsequent to this time, T₂, the bias voltage applied to thephotodetector 103 may start to increase as shown by the increase in thefunction 152. The function 152 may continue to increase over the timeperiod ΔT₃ (which may represent a portion of a time period during whichreturn light received at the photodetector 103 may originate from thelight pulse 106 traversing the environment 108) towards the upperthreshold value 159. The example function 152 may eventually peak at theupper threshold value 159 at time T₄, which may correspond to a timethat corresponds to the photodetector 103 receiving return light thatmay originate from the light pulse 106 reflecting from an object ofinterest in the environment 108. For example, as depicted in FIG. 1A,the object of interest may be the vehicle 107 c. In some instances, thefunction 152 may have been intentionally defined by a user to include apeak at this time so that the gain of the photodetector 103 may behighest when it is likely that the light pulse 106 will be received bythe photodetector 103 subsequent to reflecting from the object ofinterest 107 c in the environment 108. For example, such a peak may bechosen so that the photodetector 103 is most sensitive to return lightfrom the particular region of interest designated by a user or the LIDARsystem 101. This may allow the LIDAR system 101 to capture the mostamount of information from this region of interest relative to otherareas of the environment 108. Subsequent to this peak of the function152, the bias voltage may be depicted as decreasing over a period oftime, ΔT₅. The period of time ΔT₅ may include return light pulses beingreceived at the photodetector 103 that may originate from the lightpulse 106 traversing the environment 108 beyond the object of interest107 c. Ultimately, the light pulse 106 may reach the maximum range ofthe photodetector. As described above, the bias voltage of thephotodetector 103 may again be dropped to at or below the lowerthreshold value 156 at a time T₆ (which may correspond to a time atwhich any return light received by the photodetector 106 may originatefrom a light pulse 106 reflecting from an object at the maximum range ofthe photodetector 103. in order to avoid range aliasing. This process100 may then be repeated iteratively using either the same function 152(for example in an open loop system), or a varying function (for examplein a closed-loop system). Furthermore, it should be noted that whileFIG. 1B provides an example of a user-defined function 152 that may beused to adjust the gain of the photodetector 103, any other type offunction could similarly be used to increase and/or decrease the gain ofthe photodetector 103 at varying levels and at varying times. Forexample, the function may steadily increase until the maximum detectionrange of the detector device 103, at which point the bias voltage may bedropped to below the lower threshold bias voltage. Another exampleuser-defined function 175 is shown in FIG. 1C, which depicts a squarewave user-defined function 175 that transitions between the lowerthreshold and upper threshold instantaneously at various times. Again,this user-defined function 175 depicted in FIG. 1C is merely anotherexemplification of a user-defined function, and any other type ofuser-defined function may be applicable as well.

Illustrative Control Circuitry

FIGS. 2A-2C depict exemplary circuits that may be used to adjust a biasvoltage applied to a photodetector (for example, photodetector 103described with respect to FIG. 1A, as well as any other photodetector ordetecting device as described herein). That is, the exemplary circuitsmay be used to perform the gain adjustments described herein (forexample, at least with respect to FIGS. 1A and 1B). FIG. 2A may depict afirst example circuit 200. The first example circuit 200 may include atleast a controller 202, a digital to analog converter (DAC) 204, abuffer 210, and/or a photodetector 212. In some embodiments, thecontroller 200 may be the same as controller 105 described with respectto FIG. 1A and/or computing portion 413 described with respect to FIG. 4. The controller 202 be used to generate an output signal used tocontrol the bias voltage of the photodetector 212. For example, thecontroller 202 may store information about a user-defined function (forexample, the user defined function described with respect to FIG. 1B, aswell as any other user-defined function described herein) that may beused to control the bias voltage applied to the photodetector 212. Thecontroller 202 may use this function to determine what signal to outputthat will result in the appropriate bias voltage being applied to thephotodetector 212 based on an amount of time that has passed since alight pulse was emitted from an emitting device of the LIDAR system. Thesignal output may be a digital output signal and may be transmitted tothe DAC 204. The DAC 204 may receive the digital signal and may convertthe digital output signal to an analog signal that may then be providedto the photodetector 212 to adjust the bias voltage of the photodetector212. Before reaching the photodetector 212, the analog output signal ofthe DAC 204 may also pass through a buffer 210. In some embodiments, thebuffer 210 may be included because the first example circuit 200 mayhave to contend with the fact that the DAC 204 may not producesufficient power to drive a load directly. The buffer 210 may thus takethe voltage provided by the DAC 204 and output the same voltage withsignificantly higher current driving capabilities.

FIG. 2B may depict a second example circuit 250. Similar to the firstexample circuit 200, the second example circuit 250 may also include acontroller 252, DAC 254, and a photodiode 260. However, the secondexample circuit 250 may differ from the first example circuit 200 inthat it may also include a power amplifier (PA) 256 instead of a buffer210. This second example circuit 250 may be faster in its response andalso may pass AC voltages instead of DC voltages. In the second examplecircuit 250, the photodiode may be powered by a ‘nominal’ bias voltage(the nominal bias voltage may be a bias voltage that the photodiode 260may primarily operate at as a baseline, for example), and the DAC 254and PA 256 may provide ‘additive’ voltages to that nominal bias voltagein an AC sense via capacitive coupling 258. Under normal circumstances,the bias voltage may be at nominal, but when the DAC 254 and PA 256change their voltage rapidly, that rapid voltage change may cross thecapacitive coupling 258 and drag the bias voltage seen by the photodiode260 up or down momentarily. Some benefits of this may be that the DAC254 and PA 256 may not have to swing enormous voltages, and instead mayonly have to swing the amount of voltage required to change thephotodiode bias (or even just half of that based on the value of thenominal bias voltage). The amount of time the voltage is swung may bedictated by the frequency of the DAC 254 and/or PA 256 signal and thecutoff frequency of the capacitive coupling. However, the amount of timea changed voltage needs to be held may not be of particular concernbecause the second example circuit 250 may only need to hold chargesbased on emitted light traveling at the speed of light.

FIG. 2C may depict a third example circuit 275. As depicted in FIG. 2C,the third example circuit 275 may use a multiplexor 282 to produce adiscrete level gain waveform. The multiplexor 282 may be used in placeof a DAC (for example DAC 204 and/or DAC 254) Similar to FIGS. 2A-2B,the third example circuit 275 may include a controller 280 for producingoutput signals. However, in the third example circuit 275, thecontroller may send a signal to the multiplexor 282 through a selectioninput 286. The signal provided to the selection input 286 may indicateto the multiplexor 282, which one or more input lines 284 (for exampleinput line 284 a and/or input line 284 b and/or any other number ofinput lines) to choose to provide as an output 287 to the photodiode288.

Illustrative Methods

FIG. 3 is an example method 300 for intra-shot dynamic adjustment ofLIDAR detector gain in accordance with one or more example embodimentsof the disclosure.

At block 302 of the method 300 in FIG. 3 , the method may includeemitting, by an optical ranging system at a first time, a first lightpulse. The laser, for example, may be the same as the emitting device102 described with respect to FIG. 1A, or any other emitting and/oremitter device described herein.

Block 304 of the method 300 may include increasing, after the firsttime, a sensitivity of a photodetector of the optical ranging systemfrom a first sensitivity at the first time to a second sensitivity at asecond time. In some embodiments, the gain of the photodetector may beincreased by increasing the bias voltage that is applied to thephotodetector. Increasing this bias voltage may take the photodetectorout of its linear mode of operation (operating with a linear gain),which may effectively “unblind” the photodetector and allow it toregister returning light from the environment.

In some instances, the gain of the receiver may be increased based on aparticular function (an example of a function may be depicted in FIGS.1B and 1C described above). The function may define what the gain shouldbe set to at any given time in the timeframe between the emitted lightentering the environment and traversing towards the maximum detectingrange of the photodetector. This function may be user-defined and mayeither be fixed or may change with successive shots. For example, thegain of the detector may be dynamically altered over time instead ofsimply being increased to a maximum value immediately following theemitted light entering the environment. As a first example, the gain maybe steadily increased as the time since the emitted light exited theLIDAR system also increases (up until the time at which the emittedlight may reach the maximum detection range of the LIDAR system, and thegain detector may be brought below the threshold again as describedabove). As a second example, the gain may be increased to a maximumvalue at a point before the maximum range, and then may be decreased.That is, the gain may be increased to a maximum value at a particularregion of interest. For example, it may be desirable to ensure that thedetector is more sensitive to particular regions in the environment ofthe LIDAR system for a number of reasons. As a few non-limitingexamples, there may be a known object of interest in the region or itmay not be known if objects are in the region, but it may be desired todetermine if objects do exist. As a third example, the gain may bealtered based on external factors. For example, one external factor mayinclude the ambient light of the LIDAR system (for example the gain maybe minimized when the ambient light is greater during a bright day). Theabove examples are not intended to be limiting, and the gain of thephotodetector may be dynamically adjusted based on any other form ofuser-defined function as well.

Block 306 of the method 300 may include decreasing the sensitivity ofthe photodetector of the optical ranging system from the secondsensitivity at third time to the first sensitivity at a fourth time,wherein the fourth time is after the photodetector receives return lightbased on the first light pulse. In some embodiments, as described above,the gain of the photodetector may be reduced by reducing a bias voltagethat is applied to the photodetector. The gain may be based on the biasvoltage that is applied to the photodetector, so decreasing the biasvoltage may result in a corresponding reduction in the gain of thephotodetector. Setting the gain of the photodetector to be below thisthreshold value may result in the photodetector operating with a lineargain. This may be in contrast to operation of a photodetector in GeigerMode, for example, which may involve the photodetector operating at amuch higher gain. For example, the bias voltage may be reduced to 20V orlower. Operation of the photodetector in linear mode may effectivelyresult in the photodetector being effectively “blind” to any returninglight. The effective blinding of the photodetector during thisparticular time frame may serve to prevent the detector from detectingany return photons that may have been reflected internally to the LIDARsystem. As described above, such returns may be difficult to distinguishfrom returns that originate from low-reflective objects close to theLIDAR system. Thus, these internal reflections may result in undesirableinformation for the LIDAR system.

An example of a specific type of region of interest for which dynamicgain adjustment may be performed may be a region that includes fog orexhaust gas from another vehicle. Return light from the region may be avery bright return, which may provide an indication that the regionincludes the fog or exhaust gas. Subsequently to detecting this verybright return, the gain of the photodetector may be decreased throughthat bright region and increased again once beyond the region. This mayallow the photodetector to have increased sensitivity to what isimmediately behind the bright object (behind the fog and/or exhaustgas). For example, example at five meters from the photodetector, theremay be a region including steam coming out of an exhaust pipe and at sixmeters, there may be a person standing (behind steam from theperspective of the LIDAR system. The steam from the exhaust causes avery bright return and the photodetector may become saturated and thusunable to detect the person at six meters. Based on this, the gain maybe decreased for return light originating from five meters away (wherethe steam is), and ramped back up at 5.5 meters or some distance beyondwhere the steam exists at five meters away.

In some embodiments, the reduction in bias voltage that is applied tothe photodetector may be performed using a number of different methods.One example method may include using a high-speed digital to analogconverter (DAC) to produce a continuous gain waveform. A second examplemethod may include an analog multiplexor with two or more voltageselections for a discrete level gain waveform. Examples of circuitrythat may be used for each of these methods may be described above withreference to FIGS. 2A-2C. Additionally, these two examples should not betaken as non-limiting, and any number of additional methods fordynamically changing the applied bias voltage may also be used.

Block 306 of the method 300 may include emitting, by the optical rangingsystem at the fourth time, a second light pulse. Thus, the sensitivityof the photodetector may be at the first sensitivity at the time thesecond light pulse is emitted. This may prevent the photodetector fromdetecting return light that is reflected from internal components of theLIDAR system, avalanching, and entering a recovery period when theemitted light exits the LIDAR system and enters the environment. Thismay prevent the photodetector from being effectively blind to shortrange reflections from objects in the environment, as the recoveryperiod may last for up to tens of nanoseconds.

The operations described and depicted in the illustrative process flowof FIG. 3 may be carried out or performed in any suitable order asdesired in various example embodiments of the disclosure. Additionally,in certain example embodiments, at least a portion of the operations maybe carried out in parallel. Furthermore, in certain example embodiments,less, more, or different operations than those depicted in FIG. 3 may beperformed.

Example Lidar System

FIG. 4 illustrates an example LIDAR system 400, in accordance with oneor more embodiments of this disclosure. The LIDAR system 400 may berepresentative of any number of elements described herein, such as theLIDAR system 100 described with respect to FIG. 1A, as well as any otherLIDAR systems described herein. The LIDAR system 400 may include atleast an emitter portion 401, a detector portion 405, and a computingportion 413.

In some embodiments, the emitter portion 401 may include at least one ormore emitter(s) 402 (for simplicity, reference may be made hereinafterto “an emitter,” but multiple emitters could be equally as applicable)and/or one or more optical element(s) 404. An emitter 402 may be adevice that is capable of emitting light into the environment. Once thelight is in the environment, it may travel towards an object 412. Thelight may then reflect from the object and return towards the LIDARsystem 400 and be detected by the detector portion 405 of the LIDARsystem 400 as may be described below. For example, the emitter 402 maybe a laser diode as described above. The emitter 402 may be capable ofemitting light in a continuous waveform or as a series of pulses. Anoptical element 404 may be an element that may be used to alter thelight emitted from the emitter 402 before it enters the environment. Forexample, the optical element 404 may be a lens, a collimator, or awaveplate. In some instances, the lens may be used to focus the emitterlight. The collimator may be used to collimate the emitted light. Thatis, the collimator may be used to reduce the divergence of the emitterlight. The waveplate may be used to alter the polarization state of theemitted light. Any number or combination of different types of opticalelements 404, including optical elements not listed herein, may be usedin the LIDAR system 400.

In some embodiments, the detector portion 405 may include at least oneor more detector(s) 406 (for simplicity, reference may be madehereinafter to “a detector,” but multiple detectors could be equally asapplicable) and/or one or more optical elements 408. The detector may bea device that is capable of detecting return light from the environment(for example light that has been emitted by the LIDAR system 400 andreflected by an object 412). For example, the detectors may bephotodiodes. The photodiodes may specifically include AvalanchePhotodiodes (APDs), which in some instances may operate in Geiger Mode.However, any other type of photodetector may also be used. Thefunctionality of the detector 406 in capturing return light from theenvironment may serve to allow the LIDAR system 100 to ascertaininformation about the object 412 in the environment. That is, the LIDARsystem 100 may be able to determine information such as the distance ofthe object from the LIDAR system 100 and the shape and/or size of theobject 412, among other information. The optical element 408 may be anelement that is used to alter the return light traveling towards thedetector 406. For example, the optical element 408 may be a lens, awaveplate, or filter such as a bandpass filter. In some instances, thelens may be used to focus return light on the detector 406. Thewaveplate may be used to alter the polarization state of the returnlight. The filter may be used to only allow certain wavelengths of lightto reach the detector (for example a wavelength of light emitted by theemitter 402). Any number or combination of different types of opticalelements 408, including optical elements not listed herein, may be usedin the LIDAR system 400.

In some embodiments, the computing portion may include one or moreprocessor(s) 414 and memory 416. The processor 414 may executeinstructions that are stored in one or more memory devices (referred toas memory 416). The instructions can be, for instance, instructions forimplementing functionality described as being carried out by one or moremodules and systems disclosed above or instructions for implementing oneor more of the methods disclosed above. The processor(s) 414 can beembodied in, for example, a CPU, multiple CPUs, a GPU, multiple GPUs, aTPU, multiple TPUs, a multi-core processor, a combination thereof, andthe like. In some embodiments, the processor(s) 414 can be arranged in asingle processing device. In other embodiments, the processor(s) 414 canbe distributed across two or more processing devices (for examplemultiple CPUs; multiple GPUs; a combination thereof; or the like). Aprocessor can be implemented as a combination of processing circuitry orcomputing processing units (such as CPUs, GPUs, or a combination ofboth). Therefore, for the sake of illustration, a processor can refer toa single-core processor; a single processor with software multithreadexecution capability; a multi-core processor; a multi-core processorwith software multithread execution capability; a multi-core processorwith hardware multithread technology; a parallel processing (orcomputing) platform; and parallel computing platforms with distributedshared memory. Additionally, or as another example, a processor canrefer to an integrated circuit (IC), an ASIC, a digital signal processor(DSP), a FPGA, a PLC, a complex programmable logic device (CPLD), adiscrete gate or transistor logic, discrete hardware components, or anycombination thereof designed or otherwise configured (for examplemanufactured) to perform the functions described herein.

The processor(s) 414 can access the memory 416 by means of acommunication architecture (for example a system bus). The communicationarchitecture may be suitable for the particular arrangement (localizedor distributed) and type of the processor(s) 414. In some embodiments,the communication architecture 406 can include one or many busarchitectures, such as a memory bus or a memory controller; a peripheralbus; an accelerated graphics port; a processor or local bus; acombination thereof; or the like. As an illustration, such architecturescan include an Industry Standard Architecture (ISA) bus, a Micro ChannelArchitecture (MCA) bus, an Enhanced ISA (EISA) bus, a Video ElectronicsStandards Association (VESA) local bus, an Accelerated Graphics Port(AGP) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Expressbus, a Personal Computer Memory Card International Association (PCMCIA)bus, a Universal Serial Bus (USB), and or the like.

Memory components or memory devices disclosed herein can be embodied ineither volatile memory or non-volatile memory or can include bothvolatile and non-volatile memory. In addition, the memory components ormemory devices can be removable or non-removable, and/or internal orexternal to a computing device or component. Examples of various typesof non-transitory storage media can include hard-disc drives, zipdrives, CD-ROMs, digital versatile disks (DVDs) or other opticalstorage, magnetic cassettes, magnetic tape, magnetic disk storage orother magnetic storage devices, flash memory cards or other types ofmemory cards, cartridges, or any other non-transitory media suitable toretain the desired information and which can be accessed by a computingdevice.

As an illustration, non-volatile memory can include read only memory(ROM), programmable ROM (PROM), electrically programmable ROM (EPROM),electrically erasable programmable ROM (EEPROM), or flash memory.Volatile memory can include random access memory (RAM), which acts asexternal cache memory. By way of illustration and not limitation, RAM isavailable in many forms such as synchronous RAM (SRAM), dynamic RAM(DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM),enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM(DRRAM). The disclosed memory devices or memories of the operational orcomputational environments described herein are intended to include oneor more of these and/or any other suitable types of memory. In additionto storing executable instructions, the memory 416 also can retain data.

Each computing device 400 also can include mass storage 417 that isaccessible by the processor(s) 414 by means of the communicationarchitecture 406. The mass storage 417 can include machine-accessibleinstructions (for example computer-readable instructions and/orcomputer-executable instructions). In some embodiments, themachine-accessible instructions may be encoded in the mass storage 417and can be arranged in components that can be built (for example linkedand compiled) and retained in computer-executable form in the massstorage 417 or in one or more other machine-accessible non-transitorystorage media included in the computing device 400. Such components canembody, or can constitute, one or many of the various modules disclosedherein. Such modules are illustrated as detector gain adjustment module420.

The detector gain adjustment module 420 including computer-executableinstructions, code, or the like that responsive to execution by one ormore of the processor(s) 414 may perform functions including adjustingthe gain of the detector 406 as described herein. For example, the gainadjustment module 420 may be used to provide a signal to change the biasvoltage applied to the detector 406 as described herein. Additionally,the functions may include execution of any other methods and/orprocesses described herein.

It should further be appreciated that the LIDAR system 400 may includealternate and/or additional hardware, software, or firmware componentsbeyond those described or depicted without departing from the scope ofthe disclosure. More particularly, it should be appreciated thatsoftware, firmware, or hardware components depicted as forming part ofthe computing device 400 are merely illustrative and that somecomponents may not be present or additional components may be providedin various embodiments. While various illustrative program modules havebeen depicted and described as software modules stored in data storage,it should be appreciated that functionality described as being supportedby the program modules may be enabled by any combination of hardware,software, and/or firmware. It should further be appreciated that each ofthe above-mentioned modules may, in various embodiments, represent alogical partitioning of supported functionality. This logicalpartitioning is depicted for ease of explanation of the functionalityand may not be representative of the structure of software, hardware,and/or firmware for implementing the functionality. Accordingly, itshould be appreciated that functionality described as being provided bya particular module may, in various embodiments, be provided at least inpart by one or more other modules. Further, one or more depicted modulesmay not be present in certain embodiments, while in other embodiments,additional modules not depicted may be present and may support at leasta portion of the described functionality and/or additionalfunctionality. Moreover, while certain modules may be depicted anddescribed as sub-modules of another module, in certain embodiments, suchmodules may be provided as independent modules or as sub-modules ofother modules.

Although specific embodiments of the disclosure have been described, oneof ordinary skill in the art will recognize that numerous othermodifications and alternative embodiments are within the scope of thedisclosure. For example, any of the functionality and/or processingcapabilities described with respect to a particular device or componentmay be performed by any other device or component. Further, whilevarious illustrative implementations and architectures have beendescribed in accordance with embodiments of the disclosure, one ofordinary skill in the art will appreciate that numerous othermodifications to the illustrative implementations and architecturesdescribed herein are also within the scope of this disclosure.

Certain aspects of the disclosure are described above with reference toblock and flow diagrams of systems, methods, apparatuses, and/orcomputer program products according to example embodiments. It will beunderstood that one or more blocks of the block diagrams and flowdiagrams, and combinations of blocks in the block diagrams and the flowdiagrams, respectively, may be implemented by execution ofcomputer-executable program instructions. Likewise, some blocks of theblock diagrams and flow diagrams may not necessarily need to beperformed in the order presented, or may not necessarily need to beperformed at all, according to some embodiments. Further, additionalcomponents and/or operations beyond those depicted in blocks of theblock and/or flow diagrams may be present in certain embodiments.

Accordingly, blocks of the block diagrams and flow diagrams supportcombinations of means for performing the specified functions,combinations of elements or steps for performing the specifiedfunctions, and program instruction means for performing the specifiedfunctions. It will also be understood that each block of the blockdiagrams and flow diagrams, and combinations of blocks in the blockdiagrams and flow diagrams, may be implemented by special-purpose,hardware-based computer systems that perform the specified functions,elements or steps, or combinations of special-purpose hardware andcomputer instructions.

What has been described herein in the present specification and annexeddrawings includes examples of systems, devices, techniques, and computerprogram products that, individually and in combination, permit theautomated provision of an update for a vehicle profile package. It is,of course, not possible to describe every conceivable combination ofcomponents and/or methods for purposes of describing the variouselements of the disclosure, but it can be recognized that many furthercombinations and permutations of the disclosed elements are possible.Accordingly, it may be apparent that various modifications can be madeto the disclosure without departing from the scope or spirit thereof. Inaddition, or as an alternative, other embodiments of the disclosure maybe apparent from consideration of the specification and annexeddrawings, and practice of the disclosure as presented herein. It isintended that the examples put forth in the specification and annexeddrawings be considered, in all respects, as illustrative and notlimiting. Although specific terms are employed herein, they are used ina generic and descriptive sense only and not for purposes of limitation.

As used in this application, the terms “environment,” “system,” “unit,”“module,” “architecture,” “interface,” “component,” and the like referto a computer-related entity or an entity related to an operationalapparatus with one or more defined functionalities. The terms“environment,” “system,” “module,” “component,” “architecture,”“interface,” and “unit,” can be utilized interchangeably and can begenerically referred to functional elements. Such entities may be eitherhardware, a combination of hardware and software, software, or softwarein execution. As an example, a module can be embodied in a processrunning on a processor, a processor, an object, an executable portion ofsoftware, a thread of execution, a program, and/or a computing device.As another example, both a software application executing on a computingdevice and the computing device can embody a module. As yet anotherexample, one or more modules may reside within a process and/or threadof execution. A module may be localized on one computing device ordistributed between two or more computing devices. As is disclosedherein, a module can execute from various computer-readablenon-transitory storage media having various data structures storedthereon. Modules can communicate via local and/or remote processes inaccordance, for example, with a signal (either analogic or digital)having one or more data packets (for example data from one componentinteracting with another component in a local system, distributedsystem, and/or across a network such as a wide area network with othersystems via the signal).

As yet another example, a module can be embodied in or can include anapparatus with a defined functionality provided by mechanical partsoperated by electric or electronic circuitry that is controlled by asoftware application or firmware application executed by a processor.Such a processor can be internal or external to the apparatus and canexecute at least part of the software or firmware application. Still inanother example, a module can be embodied in or can include an apparatusthat provides defined functionality through electronic componentswithout mechanical parts. The electronic components can include aprocessor to execute software or firmware that permits or otherwisefacilitates, at least in part, the functionality of the electroniccomponents.

In some embodiments, modules can communicate via local and/or remoteprocesses in accordance, for example, with a signal (either analog ordigital) having one or more data packets (for example data from onecomponent interacting with another component in a local system,distributed system, and/or across a network such as a wide area networkwith other systems via the signal). In addition, or in otherembodiments, modules can communicate or otherwise be coupled viathermal, mechanical, electrical, and/or electromechanical couplingmechanisms (such as conduits, connectors, combinations thereof, or thelike). An interface can include input/output (I/O) components as well asassociated processors, applications, and/or other programmingcomponents.

Further, in the present specification and annexed drawings, terms suchas “store,” “storage,” “data store,” “data storage,” “memory,”“repository,” and substantially any other information storage componentrelevant to the operation and functionality of a component of thedisclosure, refer to memory components, entities embodied in one orseveral memory devices, or components forming a memory device. It isnoted that the memory components or memory devices described hereinembody or include non-transitory computer storage media that can bereadable or otherwise accessible by a computing device. Such media canbe implemented in any methods or technology for storage of information,such as machine-accessible instructions (for example computer-readableinstructions), information structures, program modules, or otherinformation objects.

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainimplementations could include, while other implementations do notinclude, certain features, elements, and/or operations. Thus, suchconditional language generally is not intended to imply that features,elements, and/or operations are in any way required for one or moreimplementations or that one or more implementations necessarily includelogic for deciding, with or without user input or prompting, whetherthese features, elements, and/or operations are included or are to beperformed in any particular implementation.

That which is claimed is:
 1. A method comprising: emitting, by anemitting device of an optical ranging system at a first time, a firstlight pulse; increasing, after the first time, a sensitivity of aphotodetector of the optical ranging system from a first sensitivity ata second time to a second sensitivity at a third time; decreasing, afterthe third time, the sensitivity of the photodetector of the opticalranging system from the second sensitivity to the first sensitivity at afourth time, wherein the fourth time is after the photodetector receivesa return light based on the first light pulse; and emitting, by theoptical ranging system at a fifth time after the fourth time, a secondlight pulse.
 2. The method of claim 1, wherein the photodetector isblind to return light at and below the first sensitivity.
 3. The methodof claim 1, wherein the photodetector is able to detect the return lightbeyond the first sensitivity.
 4. The method of claim 1, wherein thethird time is based on a time at which the return light is detected bythe photodetector, and wherein the return light is originated from aregion of interest in an environment.
 5. The method of claim 1, whereinincreasing the sensitivity of the photodetector is based on an amount ofambient light in an environment.
 6. The method of claim 1, return lightis originated from a maximum detection distance of the optical rangingsystem.
 7. The method of claim 1, wherein decreasing the sensitivity ofthe photodetector is performed using at least one of: a high-speeddigital-to-analog converter or a multiplexor with two or more voltageselections for a discrete level sensitivity waveform.
 8. The method ofclaim 1, wherein the photodetector is an avalanche photodiode.
 9. Asystem comprising: an optical ranging system; a processor; and a memorystoring computer-executable instructions, that when executed by theprocessor, cause the processor to: emit, by the optical ranging systemat a first time, a first light pulse; increase, after the first time, asensitivity of a photodetector of the optical ranging system from afirst sensitivity at a second time to a second sensitivity at a thirdtime; decrease, after the third time, the sensitivity of thephotodetector of the optical ranging system from the second sensitivityto the first sensitivity at a fourth time, wherein the fourth time isafter the photodetector receives a return light based on the first lightpulse; and emit, by the optical ranging system at a fifth time after thefourth time, a second light pulse.
 10. The system of claim 9, whereinthe photodetector is blind to return light at and below the firstsensitivity.
 11. The system of claim 9, wherein the photodetector isable to detect the return light beyond the first sensitivity.
 12. Thesystem of claim 9, wherein the third time is based on a time at whichthe return light is detected by the photodetector, and wherein thereturn light is originated from a region of interest in an environment.13. The system of claim 9, wherein the computer-executable instructionsfurther cause the processor to adjust the sensitivity of thephotodetector based on an amount of ambient light in an environment. 14.The system of claim 9, wherein the return light is originated from amaximum detection distance of the optical ranging system.
 15. The systemof claim 9, wherein decreasing the sensitivity of the photodetector isperformed using at least one of: a high-speed digital-to-analogconverter or a multiplexor with two or more voltage selections for adiscrete level sensitivity waveform.
 16. The system of claim 9, whereinthe photodetector is an avalanche photodiode.
 17. The method of claim 1,wherein the second time corresponds to a time at which photons of thefirst pulse reflected internally in the optical ranging system arereceived at the photodetector.
 18. The method of claim 1, whereinincreasing or decreasing the sensitivity of the photodetector is basedon a user-defined function.
 19. The system of claim 9, wherein thesecond time corresponds to a time at which photons of the first pulsereflected internally in the optical ranging system are received at thephotodetector.
 20. The system of claim 9, wherein thecomputer-executable instructions comprises a user-defined function,wherein the sensitivity of the photodetector is increased or decreasedbased on the user-defined function.